An inverter heat pump uses a variable-speed compressor rather than a single-speed one. This allows the system to operate at different output levels rather than only on or off, making it more efficient and quieter than conventional systems.
How Does an Inverter Heat Pump Work?
Inverter heat pumps use several key components to deliver heating and cooling efficiently. The core component is the variable-speed compressor, which adjusts its speed based on heating or cooling requirements, running slowly when demand is low and speeding up when demand is high. A refrigerant circulates through a closed loop between the indoor and outdoor units, transferring heat into or out of the home, and inverter technology adjusts the amount of refrigerant flowing at any given time. A reversing valve reverses the refrigerant’s flow direction, allowing the system to switch between heating and cooling modes.
Inverter heat pumps typically operate at 30% to 100% of capacity, depending on the difference between indoor conditions and the thermostat setpoint.
Inverter Heat Pump vs. Single-Stage vs. Two-Stage Units
- A single-stage heat pump works like a simple switch: either it’s running at full capacity, or it’s not running at all. This can lead to frequent cycling and noticeable temperature swings.
- A two-stage system improves this slightly by adding a reduced-capacity mode. It can handle lighter loads at a lower speed and shift to full output when needed.
- In an inverter heat pump, the compressor constantly adjusts in tiny increments to match the exact load in real time. By continuously varying compressor speed and refrigerant flow, the system delivers only the heating or cooling actually required.
Load Sizing for Inverter Heat Pump Systems
A heat pump must be sized correctly to work efficiently. As a basic guideline, many contractors estimate 1 ton of heating or cooling for every 400–600 sq. ft., so a 1,200 sq. ft. home typically uses a 2-ton (24,000 BTU) unit. Since 1 ton = 12,000 BTUs, these estimates help gauge system size, but the most accurate sizing comes from a Manual J calculation.
